1. Field of Invention
The present invention relates to treating agents for clarifying waste water containing dyes, other organic substances or a mixture thereof, processes for clarifying said waste water by using the same, and equipment for the same. More specifically, the present invention relates to treating agents for clarifying colored, scouring or dyeing waste water with high C.O.D. values discharged from textile mills by one step through adsorption and oxidative; processes for clarifying said waste water by useing the same; and equipment for the same.
2. Description of the Prior Art
Among the processes for treating scouring and dyeing waste water discharged from textile finishing mills, the most commonly used are the activated sludge process, the coagulation process and the active carbon adsorption process.
In most cases, the waste water discharged from textile finishing mills contains, other than dyes, organic substances such as sizing agents, e.g. starch, polyvinyl alcohol and C.M.C., and surfactants. In addition, dyes contained in this type of waste water are very diverse; for example, direct dyes, acid dyes, basic dyes, disperse dyes and sufur dyes. As the result, the waste water from textile finishing mills is quite diverse in property, such as C.O.D., S.S., color and foaming characteristics.
The problems involved in the activated sludge process are the large installation space required and the difficulty in operation control; the process is greatly influenced by the temperature of waste water to be treated and requires strict control of water temperature, and extreme care must be taken concerning proper air supply and other controls, which makes it difficult to be managed by unskilled operators. Furthermore, surfactants and dyes cannot be completely removed by this process.
The coagulation process also requires a large installation space for the settling tank, such as thickener. Another problem is that most surfactants and some dyes cannot be removed by coagulants.
The principal disadvantage of the active carbon adsorption process is that some dyes and organic substances cannot be adsorbed by active carbon.
As apparent from the above, it is impossible in conventional processes to successfully treat scouring and dyeing waste water containing a variety of dyes and other organic substances by one process; hence it is common practice at present to treat such kinds of waste water by combination of two or more types of processes. Even with such combination methods, complete removal of impurities contained is difficult.
Typical flow sheets of conventional processes are shown in FIGS. 1 and 2, wherein numeral 1 is the scouring and dyeing waste water to be treated, numeral 2 is pH adjustment, numeral 3 is the coagulation tank, numeral 4 is the coagulating agent, such as aluminum sulfate, numeral 5 is the settling tank, numeral 6 is the activated sludge processing tank, numeral 7 is the final settling tank, and numeral 8 is the active carbon adsorption column.
In FIG. 1, dyes are removed in coagulation tank 3, and other organic substances are treated in the activated sludge processing tank 6. Similar steps are followed also in FIG. 2, in which, however, dyes and other organic substances of extremely low concentration not removed through steps up to the final settling tank are processed in the succeeding steps.
As may be seen from these figures, the processes hitherto employed require large equipment to be installed in vast area and are very difficult to control. In addition, they suffer from poor efficiency in operation, taking about 520 minutes for the process in FIG. 1, and about 550 minutes for the process in FIG. 2, for the waste water to pass through the whole system.
Processes using waste aluminum sludge which consists mainly of aluminum oxide have been recently proposed. One example relates to a process in which waste aluminum sludge and an acidic solution are admixed to the waste water to be treated, sodium hydroxide is added to this mixture to cause coagulation, and the agglomerates thus obtained are heated at 400.degree. to 500.degree. C. (Japanese Patent Application No. 45454, 1976, Laid Open). Another example deals with a process using waste aluminum sludge heat-treated at 70.degree. to 1200.degree. C. (Japanese Patent Application No. 123487, 1974, Laid Open).
The former example uses the waste aluminum sludge as a coagulating agent and the latter utilizes it as an adsorbent. Hence, they are not free from the disadvantages that large equipment and large installation space are required and that other types of processes must be used in combination.